When IGMP supports multi-instance, an interface of the multicast device sends and receives protocol packets according to the instance to which the interface belongs.
When the interface of the multicast device receives an IGMP message, the multicast device needs to identify the type of the instance the interface belongs to and processes the message in the instance range. When IGMP exchanges information with other multicast protocols, IGMP only notifies these multicast protocols in the instance.
For detailed IGMP message processing, see the section IGMPv1&v2&v3.